This relates generally to systems that use multimode signaling.
Conventional signaling is either single ended or differential signaling. In single ended signaling, one wire carries one signal. The wires must be spaced to avoid cross-talk. In differential signaling, two wires carry one signal, but wire pairs must be spaced apart to avoid differential cross-talk.
In multimode signaling, the number of the wires and the number of signals may be equal or there may be an extra conductor or two to act as ground. Multimode signaling is defined as the use of linearly independent modes to reduce cross-talk. In multimode signaling, ideally cross-talk is avoided regardless of the spacing between the conductors.